Priority can be deduced using a combination of Urgency and Impact. For reference, the definitions of these terms are as follows:

Impact:a measure of the business criticality of an Incident, often equal to the extent to which an incident leads to degradation of agreed service levels. Impact is often measured by the number of people or systems affected.

Urgency:the necessary speed of solving an incident of a certain impact. A high-impact incident does not, by default, have to be solved immediately.

Priority:is expected effort. This is denoted by a number value, and is determined through assessing a combination of impact and urgency.